With the evolution of chemical, microbiological and nuclear weapons has come the development of various countermeasures to offset the deployment of such weapons of mass destruction and their aftereffects. One such development has been the countermeasure washdown systems employed on ships of the U.S. Navy and Coast Guard. These systems are activated when the ships have been exposed to chemical, microbiological or nuclear fallout from the deployment of such weapons. When activated these systems flood the entire surface of the ship with water spray which washes the fallout contamination from the ship surfaces which results in minimal exposure of the crew to the deadly effects of the weapons. These systems utilize the water from the body of water where the ship is located. It is usually fed off of the ships fire water system main with pumps supplying the various sections of the system with the necessary piping and spray heads to deliver water to the entire surface of the ship.
It is necessary that these countermeasure washdown systems be maintained in a state of readiness at all times. Prior to entering or leaving port the systems are usually made operational to determine their readiness. In many cases the system may have sections that have reduced flow rates because of blockages and it is required that they be cleaned and returned to designed operational readiness. Blockages in fresh and seawater piping systems result from corrosion and biofouling of the pipes which can occur from the residual water and its contaminants left in the system after activation. These contaminants can vary widely depending on the travels of the ship. Shallow depths and warm water are likely to be more problematic for service water systems. Macroinvertebrate to plant and animal microscopic life stages are some of the main causes of blockage. Mussels, oysters and clams are predominate species that cause biofouling. Their threadlike tentacles enable them to attach themselves to the pipe wall and to “stack up” upon themselves to cause the blockages. Other microscopic life stages such as larvae, mollusks, barnacles, sponges, tunicates, hydroids, annelids, snails, sea anemones and the like can cause settlement or attachment in the system piping resulting in blockages. Seaweed, green ribbon grass, phytoplankton, and the like can also cause undesirable blockages of the system.
Microbiologically influenced corrosion can also be present particularly when seawater, which is high in sulfate ion, is left in the system. Microbiological films and slime resulting from sulfate reducing bacteria, acid producing bacteria (which also cause corrosion of the pipe), also contribute to the operational problems of the systems. Also, blockages can result from the silt and salt deposits from the residual water employed in the testing or deployment of the countermeasure washdown system.
The above described variety of blockages present a difficult cleaning task. In addition, aluminum piping and other aluminum fabrication is used above deck on ships to decrease the weight of the vessel and to increase the stability of the ship by lowering its center of gravity. The aluminum piping systems and the degree of bends and turns in the system all add to the challenge of cleaning to maintain the operational readiness of the system for deployment. It is imperative that the chemical, biological and radiological washdown system be at 100% operational design. Therefore, the washdown system must be maintained with no blockages to reduce the design flows of the system. In the past, high pressure air or water jets have been used to pressure blast the blockage from the piping systems. This is a difficult task because of all the bends, turns, vertical and horizontal positioning of the piping configuration of the various sections of the countermeasure washdown system.
Mechanical cleaning with “snakes” or augers is also difficult and can only be used on straight runs of pipe for removing only the loose debris in the center of the pipe. High pressure air, water jet and mechanical cleaning require almost complete dismantling of the system to create access for cleaning. Such dismantling requires extended periods of unacceptable downtime for the system and the ship.
Traditional means of chemical cleaning of scale from conventional (mostly iron) pipe systems by circulating acidic cleaning solutions through sections of the system to restore flow has been described in patents. U.S. Pat. Nos. 5,360,488 and 5,885,364 (Hieatt, et al.) describe a method for cleaning sections of potable water systems with acidic cleaning solutions. U.S. Pat. No. 5,527,395 (Ludwig, et al.) describes a chemical cleaning process improvement of U.S. Pat. No. 5,360,488. U.S. Pat. No. 5,680,877 (Edstrand, et.al) describes a system (equipment) for cleaning pipe sections of a water distribution network. U.S. Pat. No. 5,873,944 (Lien, et al.) describes a method of and a system for removing blockage from pipes in vacuum waste systems. U.S. Pat. No. 5,800,629 (Fyfe, et al.) describes a process for pipe system cleaning and in-line treatment of spent pipe system cleaning solution prior to disposal. U.S. Pat. No. 5,895,763 (Temple, et al.) describes a method for the controlled removal of carbonate scale from water conduit systems. U.S. Pat. No. 6,076,536 describes a method to chemically clean and immediately passivate a water distribution system. All of the above patents are assigned to the assignee of the present invention and are hereby incorporated by reference in their entirety. None of the above patents addresses the cleaning of countermeasure washdown systems, the scale associated with the countermeasure washdown systems or the cleaning of aluminum pipe associated with countermeasure washdown systems.
Additional patents describe physical/mechanical and chemical techniques to prevent the formation of various scales from forming in water pipe systems by treating the feed water. U.S. Pat. Nos. 4,328,638; 4,462,914; 4,561,983; 4,579,665; 4,816,163; 4,857,209; 5,192,451; 5,900,157 and 6,183,646 are examples. However, such physical/mechanical and chemical techniques are impractical for countermeasure washdown systems and none have been employed in combination with countermeasure washdown systems.
In view of the above background, new methods, cleaning compositions and equipment are needed to remove blockage from chemical, biological and radiological countermeasure washdown systems on ships which contain aluminum pipe. Furthermore, needed improvements in current cleaning practices have been given a high priority so that fleet readiness may be maintained.